Welcome to our new lecture
In last lecture we have seen that Primary memory and cache
memory are parts of memory There are three types of memory
First was primary, cache and storage devices
Till last lecture we have understood about primary and cache
What are they and what are not
Which is volatile and which is non-volatile
Today we are going to talk about storage devices
Memory is a very important part of storage
Let's see what type of storage devices are available
What was used in old times
Today SSD is very popular
Solid state drive
Let's open white board and see what we are going to learn
about storage devices
Here we are going to learn about secondary storage devices
We are going to read line by line
We are going to decode them
One thing is said that reading between the line
I will try to teach you reading between the line
Because anyone can read
But we will try to break it and tell you what it means
First thing is written here
Auxiliary memory also known as auxiliary storage
Secondary storage device is known as auxiliary storage
It is also known as secondary storage It is also known as
secondary memory And external memory If anyone asks you
what is auxiliary storage
Then you should know what is secondary storage Secondary
storage is there
Secondary memory is external memory
Secondary storage device is known as secondary memory If
someone asks you what is your volatile memory You will say
that my volatile memory is RAM
Why will you call RAM or primary memory volatile
There is a reason behind it
Because if the light is switched off, the data will be lost
But this is your non-volatile memory
Why am I able to call it non-volatile memory
I am able to call it because I know that if the light is
switched off My data will not be lost
Here is the definition of it
Does not lose stored data
That is, whatever data you have stored It does not get lost
from here when the device is powered down
Device is powered down
You do not have to worry
That is not directly accessible by CPU What does it mean
I will tell you
As we try to understand from the diagram I understood that
here is my CPU There are ALU units of CPU
And there are CU units here
And here is my RAM
Which is connected like this
I call it random access memory
What happens after this
My hard disk drive is connected
Secondary storage
And what happens inside it
Files are there So now see What will I call it
Secondary storage
And here
What will we call it
Primary storage
Or primary memory
Now tell me The CPU here
And the secondary storage
Are they communicating with each other
No The files that I have
Where will it go from here
It will go inside RAM
Executable file
And my CPU What will it do
It will communicate directly from here
It communicates directly from primary memory
And not from secondary memory
So it does not directly access secondary memory Because it
is not accessed by the input output channels
Here it is written
It is not accessed by the input output channels
Means it does not do it
Through input output channels
It is an external device
If it was an internal device, it would have done it
But it is an external device, it cannot do it
RAM device as flash memory
Data can be directly deleted or changed
So what happens in this
In RAM devices
There is flash memory
Flash memory means
Install Can be directly deleted or changed
What does it mean
Earlier Xiaomi phones used to come
So what you could do
You could flash RAM directly
Flash means
Whatever is written in memory
Whatever is written in RAM
One second
Let's talk about RAM
Flash RAM
What does it mean
You are installing some extra functionality
Extra capabilities
Your device will be out of warranty
But you will get to see a lot of such features
Which you do not have
So custom ROM was very prevalent
A long time ago
When Xiaomi brought its mobile
It used to come
For computers
Now it does not come
So we have to understand
What does it mean to flash RAM
I mean to explain
It is used to store a large amount of data
At lesser cost per byte
Than primary memory
If we talk about both memory
I have primary memory
And I have secondary memory
If I said
In which memory
The cost of data will be more
I mean the cost of data per byte will be more
Then I will say that my cost will be more in storage
Is it
Or will be more of primary memory
Whatever is in my storage
Cost per byte
It always comes down
In comparison to primary memory
Because primary memory is expensive
Secondary storage is two orders of magnitude
Less expensive
Than primary storage
That is, our secondary storage
Secondary storage is always
Cheaper than primary memory
The most common forms of auxiliary memory
Are flash memory
The flash memory you will see
What will we call it?
Secondary storage
Optical device
Sorry optical disk
What will you call it?
Secondary storage
What will you call the magnetic disk?
Secondary storage
What will you call it?
Secondary storage
Let's see how it looks
Flash memory
We put it here
Flash memory
Flash memory in computer
What is coming here?
Pen drive option
What is in your computer?
USB flash drive
Flash memory
Let's see
Optical disk
Magnetic disk
See What else
See See See See See See See See See See See See that is
flash memory is faster than optical disk, faster than
magnetic disk and faster than magnetic tape as this form of
auxiliary memory does not involve any moving part why?
because flash memory does
not have any moving part so what is the problem with moving
part? like if I tell you about hard disk drive we have hard
disk drive and we have
SHD, why SHD is preferred? why HDD is not preferred? not
because it is expensive, expensive is fine but we do not
prefer hard disk drive the reason is that hard disk drive
has moving part what is the problem with moving part? if it
falls down then forget
it then it gets damaged but in solid state drive there is
no moving part if there is no moving part then we say that
this one is good so let's see when it is faster auxiliary
memory does not involve any moving parts in some laptops
such as Apple Macbook
Airline and Macbook Pro with Retina display line solid
state drive
I just told you what you get to see in them you get to see
solid state drive
that can be electrically erased and reprogrammed means
electronic non-volatile computer storage device that can be
electrically erased means if you want to erase something
then you have to do it electrically and have to reprogram
it and works without
any moving parts there are no moving parts in this example
of this are flash drives let's see memory card is there any
moving part in memory card? no is there any moving part in
solid state drive? no a version of this is implemented in
many apple notebooks
you will get to see flash memory in apple notebooks let's
talk about optical disk a storage medium from which data is
read and written by lasers what happens in optical disk
this optical disk is a storage medium from which data is
read and written by
lasers we read and write through lasers optical disk can
store much more data up to 6 gigabyte more than most
portable magnetic media means if we see the remaining
magnetic media then in comparison to that it can store more
data such as floppies example
of floppies there are three basic types of optical disk you
can see cd-rom what is cd-rom? read only memory we can't
write in this after this it becomes worm write once read
many like ram what is ram? it is p-rom where you can write
once here you can
write once eo means erasable optical disk means you can
erase it next is magnetic disk a magnetic disk is a
circular plate constructed of metal or plastic coated now
you see cd with magnetized material both sides of the disk
are used and several disks
may be staked on one spindle with redried heads available
on each surface it means what is magnetic? some are plastic
some are magnetic see here both sides of the disk are used
and several disks may be staked on one spindle you can see
magnetized material
plastic and metal coating it means a disk drive with
removable disk is called a floppy disk it means cd is
called a magnetic disk it is a type you have to understand
magnetic disk was used earlier now it is not used much
because you use either ssd or
hard disk let's talk about magnetic tapes magnetic tapes
were used long time ago a magnetic tape transport consists
of electric, mechanical and electronic components to
provide the parts and control mechanism for a magnetic tape
unit the tape itself is
a you can read it itself is a strip of plastic coated it
has the same thing plastic coated and magnetic recording
medium bits are recorded as magnetic spots on tape the
magnetic spots on the tape can be recorded 7 or 9 bits are
recorded to form a character
together it means 7 or 9 bits are used now we will see bits
wise
I will take a separate lecture in which I will tell you
these things read write heads are mounted in each track so
data can be recorded and read a sequence of characters this
is how data is stored in this you have to remember the
flash memory is the latest
one which is being used magnetic tapes were used long time
ago now it is not used much you can just remember its name
what is the use of magnetic tape to store data similarly
what is the use of magnetic disk to store data so all of
them are used to store
data but when we see first generation, second generation,
third generation fourth generation, fifth generation so at
that time at that time as an output device as an input
device so this storage was used there now what is there as
the generation changes
the latest technology is used now we will see the rest
different types of secondary storage device there exist
different types of secondary storage device each of them
suitable for a different purpose means every storage device
we have made for a different
purpose it is not that we have made anything ok you
understand we have not made anything they mainly differ in
the following aspects how they differ let's try to
understand this technology used to store data capacity of
data they can hold on the basis
of capacity technology used on the basis of technology size
of storage device portability means on the basis of size
portability of storage device means how portable it is how
you can carry it or not access time to store data means how
much time how many
fraction of seconds you can access the data how many
fraction of seconds you can read the data you can write so
what is this it is past how it will be used in different
places what technology is being used capacity will be seen
size will be seen portability
will be seen how much access time it takes that will be
seen currently the most common forms of secondary storage
device currently which are your secondary storage devices
see floppy disk
ok this is yours floppy disk is yours hard disk is yours
which you can see in your computer optical disk is yours
magnetic disk is yours solid state disk is yours what is
the work of all work of all is same storing data
understanding the characteristics
of each of them would help you choose the most appropriate
means you have to choose them according to your requirement
according to the requirement of your data like floppy disk
let's increase it a little floppy disk often referred to as
diskette diskettes
have been and are still being widely used to store data of
small size if you want to store data of small size then you
can do it in floppy disk ok you can do it in floppy disk it
looks something like this see it looks like this if we talk
about its internal
part then what happens here there is a liner, disk there
are spindle holes here ok and read write opening you can do
there is a sliding metal shutter there is a hard plastic
casing ok and write protect opening so in this way there is
some information
about its internal parts that what all what all things it
is made of so this is our example of floppy disk this is
your floppy disk and this is small size whatever data is
there if you want to store it then you can use it they are
very easy to use and
are portable you can understand from the size or how much
compact size it will be it will be portable for me ok they
consist of flat one second they consist of flat mylar
plastic disk means it is a plastic disk that rotates within
a hard plastic casing
it is kept in a hard plastic casing data is stored as
electromagnetic charge now this line becomes important for
you that how data is stored electromagnetic charge has a
metal oxide film coating coating of mylar plastic floppy
disk also contains a write
protect notch means write protection that can prevent
writing to the disk means you can't write you can't write
in the disk there exist several types of floppy disk you
can see different types of floppy disk but the most common
one is 3.5 inch floppy
disk that can store data up to a capacity of 1.44 megabyte
now it is very small in size that's why it is said that you
can store small size data in it
something like 400 type written pages a floppy drive is
required to access a floppy disk means a floppy drive is
required to access a floppy disk this is your floppy drive
you can see this in earlier laptops like DVD writer earlier
you can see floppy
drive
DVD writer can't be seen earlier you can see floppy disk
when the floppy is inserted now see this is your floppy
drive in this floppy drive this floppy disk is inserted
when the floppy is inserted in the floppy drive the sliding
metal shutter is opened
exposing the mylar plastic and a read write heads move
across the exposed disk to either store or retrieve data
this is a mechanism when it is inserted it can store or
retrieve data data is recorded on the disk in closed
concentric circle known as tracks it is stored in the form
of tracks which is called tracks let's move ahead what are
the other things this is
my tracks in floppy disk you can see these tracks in floppy
disk like this is my circle
this is my circle this is my next circle
handling them.
Otherwise, you might find yourself losing all data that you
have saved in your floppy disk.
Here are some guidelines that you need to follow regarding
floppy disk.
Avoid touching the Mylar plastic.
Do not bend the disk as this may affect the magnetic
characteristics of the disk.
Never remove a floppy while the light of floppy drive is on.
Do not touch the Mylar plastic while the light of floppy
drive is on.
Do not expose your floppy disk to extreme heat.
Keep your floppy in dedicated storage boxes.
Hard disks differ from floppy disks.
In that, they have been designed to store very high volume
of data.
In that, they have been designed to store very high volume
of data.
Currently, hard disks can store gigabyte of data.
Most of operating system are stored in hard disk.
materials application software documents images music files
that you save on your computer is stored in the hard disk
this also you can see in the hard disk now here you can see
like drive c, d drive, e drive, f drive why it is there?
means suppose your
hard disk is of 500 GB what you have done is that you have
partitioned it and you have said that this is my c drive,
this is my d drive and this is my e drive
now what is the benefit of this? I will tell you suppose
this is c drive, in c drive you have installed your
operating system and its size is suppose 100 GB, its size
is 100 GB
and its size is 200 GB and its size is 200 GB so now
suppose you have stored your reading material in e drive,
in d drive you have stored your entertainment material, in
c drive you have stored your operating system, now
operating system sometimes does
not work, sometimes window is corrupted so when you put new
window in c drive you have to remove the old one so that is
why you have to partition otherwise what will happen if you
have only one drive and operating system in it then you
have to erase all
the data and after that your windows operating system will
be installed, you can see this in my computers, locating
hard disk inside a computer, moving forward, locating the
logical hard disk of a computer is very easy and all you
have to do is double
click on the my computer.
floppy disk data is stored in the closed concentric circles
any interesting feature about hard disk apart from their
large data holding this is a feature what is the feature?
feature is that you can store large data in it is there
access time? hard disk provide fast access both for reading
and writing that is
what happens in hard disk you can access data quickly you
can read that is why it is always faster to open a document
present on a hard disk rather than a floppy
if I compare floppy with hard disk then I know that in
floppy my data will be of small size that is, the capacity
of floppy is less second thing is that my hard disk
capacity is more this is the first difference second
difference is that what I have to
read and write in this hard disk it is very fast in
comparison to floppy in floppy it is slow let's see what is
internal and external hard disk it is written that most
hard disks are specifically designed to be fixed inside a
computer that is, it is called
internal hard disk but with advances in technology and user
needed hard disk can now be connected externally to a
computer there are ports inside a computer
you can also bring an external hard disk what is the
function of external hard disk? suppose you have a 500 GB
internal hard disk and it is full now you need more data if
you want to store data you can go to the market and bring
an external hard disk
and you can connect it directly like you connect a keyboard
to a cabinet
or like you connect a charger to a computer in the same way
when you connect to this port it starts charging so you can
also connect your secondary storage as soon as you connect
it to the port you can store data inside it via USB port
what is the name
of this port? USB port external hard disks are mostly used
for backup purposes why external hard disk is used? for
backup and transferring of large amount of data let's store
a lot of data in this port which is not useful we will see
when it will be useful
both internal and external hard disk work under the same
principle it works on the same principle however external
hard disk delivers slower access time due to its USB
interfacing with a computer for data transfer what does it
mean? both internal and
external hard disks work on the same principle if your
school is far from your house then it will take more time
to reach there if your school is near to your brother's
house then it will take less time to reach there because
internal hard disk is connected
internally it is near to other components
external hard disk has to go through the port because data
transfer is slow whereas internal hard disk is fast let's
talk about optical disk how does optical disk look like?
optical disk looks like this what is this? now this is
optical disk so to connect
optical disk we need some DVD writer
we saw floppy drive in which floppy disk was used so what
is written here? music CDs compact disk form part of a
category of storage device called optical disk what we call
them? music CDs which were called compact disk form part of
category of storage
device we can call them as this kind of storage devices
later make use of light energy to store information light
energy is used to store information and very suitable to
store information of relatively high capacity you can store
information up to 700
MB in this compact disk they come in the form of a thin
plastic disk you can buy it from market it will look like
this
it is a thin plastic disk you must have brought it with a
printed label layer on one side it is printed on one side
name is written on one side movie name is written on other
side and a reflective layer on the other side on the other
side there is a reflective
layer on which a high laser beam will read and write data
what does high laser beam do? it reads and writes data
depending on the type of optical disk being used computer
system usually have access to these storage media by CD
drivers
I said CD drive you will put CD in CD drive what is this?
that is a CD drive and what is this?
CD and what do we call CD? we call CD as optical storage
that contain a special lens to read and write data on the
disk an interesting characteristic about CD drive is speed
of rotation it also rotates with speed typical speed range
from 12x to 52x the rotating speed I will read it fast
because there is so
much data there are so many numbers rotating speed
determines the rate at which data is transferred from the
computer to disk and vice versa 32x drive will transfer 4.8
MB of data per second compared of 3.6 MB of data per second
for a 24x drive if you
take 24x drive, data speed will be low if you take 32x
drive, transfer speed will be high like pen drive also 3.0,
2.0, there are such pen drives there is such thing in pen
drive if you take pen drive of 32 GB and you take pen drive
of 32 GB but one is
of 2.0 and other is of 3.0 so 3.0 drive will be faster you
should keep this thing in mind the faster the drive,
therefore the faster data can be read from the CD and used
by the computer currently there exist three basic types of
CDs you can remember
three basic types of CD that you will surely make much use
of CD ROM is read only memory you can't make changes in CD
CDR and CD RW
CD RW means you can do both read and write you can read in
CDR basically all of them have the same storage capacity
except that they differ from their read write capability if
you leave read write capability, then their work is same
CD ROM 1 now let's try to understand what is this
CD ROM stands for Compact Disc Read Only Memory we got to
know from this that we don't have to do much we got to know
that ROM is written we just read in primary memory what is
the meaning of ROM stands for Compact Disc Read Only Memory
Compact Disc Read
Only Memory
Compact Disc Read Only Memory
Erasable Disc
Erasable Disc existed for a long time now.
They are very similar to the tapes that are used in radio
cassettes player and video recorders and can still be found
in video camcorders.
Magnetic tape is very effective means for backup purpose
for large amount of data.
However, the main limitation is that data stored is a
sequential mode.
That is you may have to wait for several inches of tape to
play before you can reach the data in trust of you.
Consequently, access to the required data is slow.
Direct access on the other hand allow the user to go
directly to the piece of information without having to wait.
A clear example of direct access is when you want to play a
track on a music CD and that you only need to select the
songs you want to listen to.
Magnetic tape cartridges and streamers are usually made
mainly by micro computers where magnetic tape reels which
offer much higher backup capacity are used by mainframes.
This is the image of magnetic tape reel.
And data is stored and retrieved from them in a similar
manner as it would be from computer memory.
They come in different forms.
Sometimes under different commercial names such as USB
disk, pen drives, flash disk etc.
Some manufacturers tend to market these devices by adding
components such as mp3 players within the device and so on.
However, all of them work with very little power and
represent a reliable device having relatively good storage
capacity.
Typical storage capacity range from 32 MB to 1 GB.
Typical solid state storage device.
storage capacity range from 32 MB to 1 GB.
Typical storage capacity range from 32 MB to 1 GB.
Typical storage
capacity range from 32 MB to 1 GB. Typical storage capacity
range from 32 MB to 1 GB.
ancing and what it does is it reads and writes what is the
problem with it the problem is that if it falls then it is
over because it is a moving part after that we saw that
there is an internal and external hard disk internal hard
disk is very fast because
it is on your motherboard the external hard disk you
connect it via USB port so it is a little difficult to
transfer
I won't say difficult but it is a little slow about optical
disk we understood that the music CDs or DVDs what we call
them see it is O shaped it is not optical disk it has a
capacity of 700 MB but what is the difference between CD
and DVD
CD has a capacity of 700 MB DVD has a capacity of 4 GB like
this so for this you need a CD drive for this whatever data
is there in it if you want to write CD or read CD so you
need a CD drive if you want to write CD you need a burning
software after
that we saw CD ROM
CDR CDRW CD ROM is like if I go to the market and buy a
movie CD so what I got
I got to know that
I can put it in the category of CD ROM what is CDR if I
want to do a business CDRW I can erase or write what is DVD
we saw the trademark of DVD 4.7 to 17 GB of data it can
store we saw different types of
DVD ROM
DVDR DVDRW here you can only read here you can only record
once here you can do several times so this is the
reflective surface this surface should not have anything
how to care CD or DVD it is told here that do not keep it
in extreme temperature other
secondary devices have magnetic tapes it looks like like
radio cassettes you can see it in your video cam recorder
this is magnetic tape you can store data in it this is
solid state storage device it is of typical type it is of
small size but today's
SRG it is of big size it is of 2 TB so this is all in this
lecture we understood about storage what type of storage it
is it is floppy optical SSD SSD SSD SSD SSD SSD SSD SSD SSD
SSD SSD SSD SSD SSD hey, have you heard about the refer and
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